To study the methylation level of retinal gene promoter region in a rat model of type 1 diabetes (T1D) and investigate the correlation between DNA methylation level and retinal damage caused by T1D.

Twenty male SD rats aged 8-10 weeks were randomly divided into a control group and a T1D group using a random number table.T1D model was established via a rat tail vein injection of streptozotocin (STZ). The same volume of sodium citrate buffer was injected in the same way in the control group.Body mass of the rats was monitored before and after the injection of STZ.Blood glucose concentration of the rats was detected three days and five weeks following the injection.Methylated DNA immunoprecipitation-chip (MeDIP-chip) technology was employed to analyze the DNA methylation in the CpG islands of retinal gene promoter regions of the rats.Methylation data were compared between the two groups and subjected to Gene Ontology (GO) and pathway enrichment analyses.This study protocol was evaluated and approved by the Institutional Animal Care and Use Committee of Tianjin Medical University, and the use and care of the animals were in accordance with the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health.

Compared to the normal control group, typical deregulated metabolic syndromes were found in the T1D group.including hyperphagia, polydipsia, polyuria, and loss of body weight.According to the results of MeDIP-chip analysis, 1 478 differentially methylated gene loci were detected in the T1D group compared to the normal control group, of which 689 were hypermethylated and 789 hypomethylated.Of these differentially methylated loci 768, 365 and 345 were located in high, intermediate, and low CpG-density promoters, respectively.GO analysis showed that the differentially methylated genes were involved in some molecular functions such as protein binding.The pathway analysis revealed that the hypermethylated genes in the rats of the T1D group were associated with mitogen-activated protein kinase (MAPK) and calcium signaling pathways; whereas the hypomethylated genes were associated with MAPK, Notch, and glutamatergic synapse signaling pathways.

Methylation level of the majority of genes was altered in T1D rats.A differential methylation in the retinal gene promoter regions provides a preliminary theoretical basis for elucidating the molecular mechanism underpinning diabetic retinopathy and searching for novel therapeutic targets.

Diabetes, type 1; DNA methylation; Methylated DNA immunoprecipitation; CpG island; Diabetic retinopathy; Epigenetics; Disease model, animal